Percutaneous transluminal coronary angioplasty ("PTCA") is an established treatment for coronary artery disease. The procedure involves inserting a balloon catheter through a vascular structure to a structure site at which atherosclerotic plaque has collected on the vessel wall. (As used herein the term "vascular structure" includes arteries, veins and the coronary structures which carry blood.) The plaque is disrupted by inflating the balloon at the distal end of the catheter, thereby increasing the intraluminal diameter of the vascular structure and spreading or loosening the plaque. Disruption of the plaque ultimately reduces the restriction to the blood flow through the vascular structure. After sufficient expansion, the balloon is then collapsed and removed, and the area of disruption heals.
While the PCTA procedure is very widely used, one problem which limits its acceptability is a condition known as restenosis.
Restenosis is the development of further blockage in the intravascular structure, following otherwise successful PTCA at the angioplasty site. Restenosis is believed to be an exaggerated form of a normal healing process following the stretching; it occurs in approximately 20-50 percent of cases.
Restenosis is thought to be caused by fibrointimal proliferation of the stretched wall in which the injured cells lining the vascular structure multiply and form fibrous tissue. Fibrointimal proliferation at the vascular wall is an almost malignant phenomenon in which normal cells multiply at a high rate, thereby creating an obstruction to flow through the vascular structure.
Various techniques and devices have been proposed to deal with the problem of restenosis. These include laser, atherectomy, radio frequency and ultrasound treatments and the use of expandable stents. To date, no device has eliminated the problem of restenosis.